46 



CHEMISTRY. 



fclrmrnti limpid, has an acrid Ustc, and changes vegetable 

 bluet to green. When exposed to the air, the lime 



; S oon combine* with carbonic acid and precipitates, 

 leaving the water pure. From the experiment! of 

 Mr Dillon, it appears that cold water dissolves twice 

 at much lime as hut water. 



Lime has the property of absorbing oxygen. Sul- 

 phur and phosphorus are the only two simple com- 

 bustibles that unite with it. 



'5ulphuret. Sulphnret of lime may be formed by mixing its two 

 constituents together, and heating them in a crucible. 

 The mass has a reddish colour. In the air it be- 

 comes greenish yellow, sulphm eted hydrogen is form- 

 ed, and the mass is converted into hydrogurctcd ml 

 phuret of lime. This last compound may be formed 

 by boiling a mixture of sulphur and lime in about 

 ten times its weight of water. The solution has a 

 yellow colour, and is used for absorbing oxygen from 

 air. 



Photphu- Phosphuret of lime may be formed by passing 

 ret- phosphorus through red-hot lime in a glass tube. It 



Las a deep brown colour, and falls to powder in the 

 air. When thrown into water, bubbles of phosphu- 

 reted hydrogen gas are emitted, which take fire as 

 they separate from the liquid. 

 Lime docs not unite with azote. 

 Lime facilitates the oxidizement of several of the 

 metals. It dissolves some metallic oxides, as those 

 of mercury and lead. 



It docs not unite with the alkalies. 

 Mr Davy has lately ascertained that lime, like the 

 fixed alkalies, is a compound of oxygen and a pecn- 

 filciura. liar metal, to which he hag given the name of cnlcium. 

 He decomposed lime, by exposing a mixture of moist- 

 ened lime and red oxide of mercury to the action of 

 a galvanic battery. A globule of mercury was pla- 

 ced in the middle of the mixture. The lime was de- 

 composed, and its base united with the mercury, and 

 formed an amalgam. The mercury was distilled off 

 in glass tubes filled with the vapour of naphtha, and 

 the calcium remained behind. 



Calcium is white like silver, solid, and four or five 

 times heavier than water. When heated, it burns 

 brilliantly, and quick-lime is produced. 



SECT. II. Of Magnesia. 



Slagnetia, Magnesia was discovered about the beginning of 

 the 18th century, by a Roman canon. But little 

 was known about its nature, till Dr Black made his 

 celebrated experiments on it in 1755. 



how ob- It may be procured from the salt called sulphate 



tained. of magnesia, or Epsom sail, by dissolving the salt in 

 water, and pouring potash into the solution. A white 

 matter falls ; when washed and dried it is pure mag- 

 nesia. 



It proptr- Magnesia is a very soft light powder, with very 

 ** little taste, and destitute of smell. Its specific gra- 



vity is 2.3. It tinges vegetable blues green. It 

 does not melt in the strongest heat that can be 

 raised. 



It is not sensibly soluble in water, and has never 

 been exhibited in a crystallized form. When expo- 

 u d to the air, it attracts carbonic acid very slowly. 

 It does not combine with oxygen, nor with any of 



the simple combustibles except sulphur. The ul- Element! 

 phuret of magnesia may be formed, by mixing the , 

 two constituents, and exposing it to a moderate heat. Tj!"'*'^' 

 The result is a yellow powder slightly agglutinated. 



It does not combine with azote. 



It has no action on the metals, nor is it known to 

 combine with any of their oxides. Neither does it 

 unite with the fixed alkalies or with lime. 



Mr Davy succeeded in decomposing magnesia, by Magniow. 

 the same process that furnished him with the base of 

 lime. Like lime it is composed of oxygen and a me- 

 tal, to which the name of mngiiitnn has been given. 

 This metal is white, sinks rapidly in water, absorbs 

 oxygen when exposed to the air, and is converted in- 

 to magnesia. It decomposes water, but not nearly 

 so rapidly as the other alkaline metals, owing doubt- 

 less to the insolubility of magncsi-i. 



SECT. III. Of Bardlet. 



Barytes was discovered by Scheele in 1774. It Bamc?, 

 is usually obtained from a heavy foliated brittle mi- 

 neral, pretty common, and called ponderous spur, or ' 10W ^~ 

 su/jt/iate of barytes. This mineral is mixed with 3I " 

 charcoal powder, and exposed to a strong heat in a 

 crucible. It is then dissolved in water, and saturated 

 with nitric acid. The liquid, filtered and evapora- 

 ted, yields crystals, which being exposed to a strong 

 heat in a crucible, leave behind them an earthy mat- 

 ter, which is barytes. 



Barytes thus obtained is a greyish white porous Its proper- 

 body, and may be easily reduced to powder. Its tiei - 

 taste is more caustic than that of lime, and when 

 swallowed it acts as a violent poison. Its specific 

 gravity is 2.374. W r hen water is poured on it 

 heat is evolved, and the barytes is slacked precise- 

 ly as happens to lime. By this means it combines 

 with water, and is converted into hydrate of barylei. 



Water dissolves about 0.05 of its weight of ba- 

 rytes. The solution has an acrid taste, and tinges 

 vegetable blues green. Boiling water dissolves more 

 than half its weight of barytes. As the solution 

 cools, the barytes precipitates in crystals. 



Barytes absorbs oxygen, but does not combine 

 with any of the simple combustibles except sulphur 

 and phosphorus. The sulphuret and phosphuret of 

 barytes may be formed precisely in the same way as 

 those of lime, which they resemble in most of their 

 properties. 



Barytes is not acted on by azote. 



Barytes has no action on the metals, but it com- 

 bines with some of the metallic oxides, and forms 

 compounds hitherto scarcely examined. 



It does not combine with the alkalies, nor has it 

 much action upon lime or magnesia. 



Mr Davy has shown, that barytei, like the precc- Barium.' 

 ding earths, is a metallic oxide, being composed of 

 oxygen and a metal, to which the name of Liiriiim 

 has been given. The barium was obtained by the 

 same process as that v.hich furnished him the bases 

 of lime and magnesia. It is a white solid metal, 

 melts at a heat below redness, and in not volatilized 

 at the temperature capable of melting plate-glas*. It 

 is at least four or .'ve times hum. T than w,.ter. It 

 decomposes that liquid with great rapidity, and 



